PAOs are a class of hydrocarbons that can be manufactured by the catalytic oligomerization (polymerization to low-molecular-weight products) of linear α-olefin (LAO) monomers. These LAO monomers typically range from 1-octene to 1-dodecene, with 1-decene being a preferred material. PAO's of different viscosity grades are typically produced by the polymerization of an LAO in the presence of a polymerization catalyst such as Friedel-Crafts catalysts. These include, for example, boron trifluoride, aluminum trichloride, or boron trifluoride promoted with water, with alcohols such as ethanol, propanol, or butanol, with carboxylic acids, with esters such as ethyl acetate or ethyl propionate, or with ethers such as diethyl ether, and diisopropyl ether. Subsequent to oligomerization, the PAO products desired to be used as lubricants are typically hydrogenated in order to reduce the residual unsaturation in the polymer, generally to a level of greater than 90% hydrogenation.
Currently, PAOs are used as basestocks in premium lubricant formulations. PAOs have many advantages over conventional mineral oil or other high quality lubricants. PAOs are important lube basestocks with many excellent lubricant properties, including high viscosity index (VI) and low volatility, and are available in various viscosity ranges (Kv100 2-300 centiStokes (cSt). PAOs are often considered the best of the hydrocarbon type lubricants. However, PAOs are paraffinic hydrocarbons with low polarity. This low polarity leads to low solubility and dispersancy for polar additives or sludge generated during service. To compensate for this low polarity, lubricant formulators usually add one or multiple polar co-basestocks. Esters or alkylated naphthalene (AN) is often used in PAO formulations at 1 wt. %-50 wt. % levels to increase the fluid polarity. Therefore, there is a need for a fluid exhibiting the lubricity parameters of PAO, but with built-in polarity in order to have excellent lubrication properties without the need for a co-basestock.
Methods for the preparation of polymers from vinyl alkyl ethers have been disclosed.
In Aoshima, S. et al., Chemical Reviews, (2009), 109(11), 5245-5287, American Chemical Society, relates to a review of living cationic polymerization initiators, including the design and synthesis of a variety of new polymers, with focus on the most recent developments. Polymerization of a large number of monomers is described, with emphasis on novel monomers and preparation of block and end-functionalized polymers of various chain structures.
In U.S. Pat. No. 3,228,923, it is disclosed that polymers of vinyl alkyl ethers can be prepared using monomers comprised of ethers having the general formula H2CO═CH—O—R, where R is an alkyl radical of from 1-20 carbon atoms. It is stated that lower reaction temperatures yield a higher molecular weight polymer, and that the resulting polymers are viscous oils, sticky semi-solids or hard solids. The polymers are said to be useful as adhesives, lubrication oil additives, paint and lacquer resins, molding resins, coatings, and plasticizers/modifiers for various resins and plastics. In the only example provided, the resulting polymer was said to have particular use as an adhesive, and that “when any of the other above-identified vinyl alkyl ethers are substituted for those used in the foregoing example, substantially analogous results are obtained”.
In U.S. Pat. No. 5,691,430 there is disclosed a process for polymerizing a vinyl ether monomer which comprises contacting the vinyl ether with an initiator system of silicon dioxide and a one or more metallic oxides. The vinyl ethers which are useful in the disclosed process are said to be those monomers having the formula H2C═CH—OR, wherein R is an alkyl cycloalkyl or alkyl substituted cycloalkyl aromatic or alkyl substituted aromatic, and R is 1 to 20 carbon atoms. The polymerization initiator system is said to include silicon dioxide and one or more metallic oxides.
In U.S. Pat. No. 3,468,856 there is disclosed a process for the preparation of vinyl ether polymers by the polymerization of a vinyl ether in the presence of a multi-component catalyst system including (a) an organo aluminum compound of the general formula AlXnR3n, wherein X represents a halogen atom, R is a member selected from alkyl cycloalkyl, aryl and aryl alkyl groups, and n is an integer of 0-2, (b) a carboxylic acid anhydride, and (c) a Friedel-Crafts halide.
In Chatterjee, P. et al., Indian Journal of Chemistry (1967), 5(4), 160-2, it is disclosed that octadecyl vinyl ether is cationically polymerized in a variety of solvents with anhydrous SnCl4. The molecular weight-intrinsic viscosity relation for octadecyl vinyl ether polymers is said to be determined and the IR spectrum of the polymer recorded. It is also said that solvents with dielectric constants lower than that of the catalyst give better polymers compared with solvents with higher dielectric constants; the latter are said to give polymers having molecular weights <1000 or no polymerization at all.
In Kanazawa, A. et al., Journal of Polymer Science, Part A: Polymer Chemistry (2006), 44(19), 5795-5800, it is said that living cationic polymerization of iso-butyl vinyl ether was conducted in toluene in the presence of different Lewis acids (FeBr3, FeCl3, SnCl4, EtAlCl2) and/or in the presence of different bases (EtOAc, THF, 1,4-dioxane, and 1,3-dioxolane). Conversion, molecular weight, and polydispersity index of the resulting polymer were also said to be determined, and that basicity of base affected polymerization rate significantly. It is said that an appropriate combination of a weak Lewis base and FeCl3 realized very fast living cationic polymerization.
In JP 1993-210734, it is said that polymers with narrow molecular weight distribution (Mw/Mn) are prepared by living polymerization of vinyl or propenyl ethers by using living polymerization initiators containing a three component system of (a) HX (where X is chlorine, bromine or iodine), MeCHXOR, or EtCHXOR (where R is a hetero atom-substituted alkyl), (b) SnX4, SnX2, ZnX2, or TiX4 as Lewis acids, and (c) Ra4N+BRb4− or Ra4P+BRb4− (where Ra is a primary or secondary alkyl or aralkyl, and Rb is halo or alkyl-substituted aromatic hydrocarbyl).
In U.S. Pat. No. 3,541,015, it is disclosed that ethyl vinyl ether is copolymerized with a comonomeric compound of the formula CH2═CHOR, wherein R is phenyl or alkyl of from 3 to 30 carbon atoms to give a copolymer containing from 20 to 85 weight percent of said comonomeric compound. The resulting copolymer is said to be soluble in hydrocarbon lubricating oils and exhibits a unique combination of properties such as viscosity index.
Other published articles include Kanazawa, A. et al., Macromolecules 2009, 42, 3965-3972; Kanazawa, A. et al., Chem. Lett., 2010, 39, 1232-1237; Sawamoto, M., Prog. Polym. Sci., 1991, 16, 111-172; Aoshima, S. et al., Macromolecules, 1989, 22, 1010-1013; and Kishimoto, Y. et al., Macromolecules, 1989, 22, 3877-3882.
There is a need to provide for the synthesis of high performance PVEs using a controlled living cationic polymerization process. There is also a need for a new class of synthetic fluids containing a general chemical composition similar to PAO but with built-in oxygen functionality in the form of ether functional groups. There is further a need for PVEs with varying molecular weight, varying polarity and low molecular weight distributions (MWDs). These needs are met through applicants' present disclosure, which follows, wherein one or more vinyl ether monomers are reacted in a controlled living cationic polymerization process.